Packet switched communications networks having multiple switching nodes connected by the Ethernet are used extensively in computer based communications systems. The Ethernet is used in local area networks (LAN), for example, to interconnect or link a plurality of clients to a client server. Ethernet implementations typically transfer data packets or frames between switching nodes over a physical medium such as a twisted copper pair, coaxial cable, fiber optic cable, etc. Early Ethernet systems operated at data rates of 10-Mb/s and typically employed coaxial cables. Second generation Ethernet systems operate at 100 Mb/s and the more recent Ethernet systems known as Gigabit Ethernet operate at data rates of 1 Gigabit per second and will typically employ fiber optic cables.
The Ethernet has been standardized by the LAN Standards Committee of the IEEE under the Ethernet standard IEEE 802.3. According to this standard the Ethernet frame has a packet format which includes a preamble, source and destination address, length of data field and the data field itself. In Ethernet the data field is a variable length which can be up to 1500 bytes or octets.
The preamble frame which is an 8 octet frame is used for synchronization in the 10 Mb/s and 100 Mb/s systems. In the Gigabit Ethernet system, however, the synchronization function is not necessary because the link is always active and the synchronization is always maintained. The present invention makes use of this preamble frame by selecting portions of the unused octet for implementing a control channel between switching nodes.